Several concepts and architectures are known in the art for providing communication services over communication networks. For example, the Intelligent Network (IN) is an architectural concept that enables real-time execution of network services and customer applications in a distributed environment of interconnected computers and switching systems, such as wireline and wireless telephone networks. IN standards have been promulgated by the International Telecommunications Union (ITU-T) and by the American National Standards Institute (ANSI). The IN concept is described, for example, by Faynberg et al., in “The Development of the Wireless Intelligent Network (WIN) and Its Relation to the International Intelligent Network Standards,” Bell Labs Technical Journal, Summer, 1997, pages 57-80, which is incorporated herein by reference.
Another example of a standardized service provisioning architecture is the Internet Protocol Multimedia Subsystem (IMS) architecture. The IMS architecture is defined and described in a 3rd Generation Partnership Project (3GPP) standard entitled “Technical Specification Group Services and System Aspects; IP Multimedia Subsystem (IMS); Stage 2 (Release 7),” 3GPP TS 23.228, version 7.2.0, December 2005. This standard is available at www.3gpp.org/ftp/Specs/html-info/23228.htm. The IP multimedia core network (IM CN) subsystem enables Public Land-Mobile Network (PLMN) operators to offer their subscribers multimedia services based on and built upon Internet applications, services and protocols.
The IMS architecture is described, for example, in a whitepaper published by Lucent Technologies Inc. (Murray Hill, N.J.) entitled “IP Multimedia Subsystem (IMS) Service Architecture,” February, 2005, which is incorporated herein by reference. The whitepaper is also available at www.lucent.com/livelink/090094038005df2f_White_paper.pdf.
Signaling in IMS networks is typically performed in accordance with the well-known Session Initiation Protocol (SIP). SIP is described by Rosenberg et al., in request for comments (RFC) 3261 published by the Internet Engineering Task Force (IETF) entitled “SIP: Session Initiation Protocol,” June 2002, which is incorporated herein by reference. This RFC is also available at www.ietf.org/rfc.